<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var month = parseInt(prompt("请输入一个月份:"))
switch (parseInt((month - 1) / 3)){
    case 0:
        alert("春暖花开");
        break;
    case 1:
        alert("夏天很热");
        break;
    case 2:
        alert("秋高气爽");
        break;
    case 3:
        alert("冬天很冷");
        break;
    default:
        alert("你输入的月份有误");
        break;
}
</script>
</body>
</html>